1 第一章 信号与系统 1-1 画出下列各信号的波形【式中)()(tttr】为斜升函数。 (2 )tetft ,)( (3 ))()sin()(tttf (4 ))(sin)(ttf (5 ))(sin)(trtf (7 ))(2)(ktfk (1 0 ))(])1(1[)(kkfk 解:各信号波形为 (2 )tetft ,)( (3 ))()sin()(tttf 2 (4 ))(sin)(ttf (5 ))(sin)(trtf (7 ))(2)(ktfk (1 0 ))(])1(1[)(kkfk 3 1-2 画出下列各信号的波形[式中)()(tttr为斜升函数]。 (1 ))2()1(3)1(2)(ttttf (2 ))2()1(2)()(trtrtrtf (5 ))2()2()(ttrtf (8 ))]5()([)(kkkkf (1 1 ))]7()()[6sin()(kkkkf (1 2 ))]()3([2)(kkkfk 解:各信号波形为 (1 ))2()1(3)1(2)(ttttf (2 ))2()1(2)()(trtrtrtf 4 (5 ))2()2()(ttrtf (8 ))]5()([)(kkkkf (1 1 ))]7()()[6sin()(kkkkf 5 (1 2 ))]()3([2)(kkkfk 1-3 写出图1-3 所示各波形的表达式。 6 1-4 写出图1-4 所示各序列的闭合形式表达式。 7 1-5 判别下列各序列是否为周期性的。如果是,确定其周期。 (2 ))63cos()443cos()(2kkkf (5 ))sin(2cos3)(5tttf 解: 8 1-6 已知信号)(tf的波形如图1-5 所示,画出下列各函数的波形。 (1 ))()1(ttf (2 ))1()1(ttf (5 ))21(tf (6 ))25.0(tf (7 )dttdf)( (8 )dxxft)( 解:各信号波形为 9 (1 ))()1(ttf (2 ))1()1(ttf (5 ))21(tf (6 ))25.0(tf 10 (7 )dttdf)( (8 )dxxft)( 1-7 已知序列)(kf的图形如图1-7 所示,画出下列各序列的图形。 (1 ))()2(kkf (2 ))2()2(kkf (3 ))]4()()[2(kkkf (4 ))2(kf (5 ))1()2(kkf (6 ))3()(kfkf 解: 11 1-9 已知信号的波形如图1-11 所示,分别画出)(tf和dttdf )(的波形。 1 2 解:由图1-11 知,)3(tf的波形如图1-12(a)所示()3(tf波形是由对 )23(tf的波形展宽为原来的两倍而得)。将)3(tf的波形反转而得到)3( tf的波形,如图1-12(b)所示。再将)3( t...